A chip on film (COF) base applied to an electronic device such as a flat panel display such as an LCD or a mobile device performs a function of allowing a circuit chip and a circuit wiring to be disposed in a region where bending is performed due to flexible characteristics. Such a COF base may increase a degree of freedom in a design of electronic devices and is widely used for various shapes and structures of bent electronic devices.
However, in the COF base, cracks may occur in a process of a repeated bending action or coupling in a bent state of a circuit pattern formed on a base film, or a problem that a metal pattern layer may be broken due to a tensile force generated at the time of bending the circuit pattern may occur.
Referring to FIG. 1, FIG. 1 is a view of an example of application to a product in which a COF base is used. As shown in FIG. 1, a COF base 3 is used to constitute a device including a display panel 1. That is, the COF base 3 may function to electrically connect the display panel 1 and a FPCB 2, and may be bent and connected as shown in FIG. 1 in order to secure a space inside a device. In this case, an IC chip 4 may be further mounted on the COF base 3.
In such a structure, recently, as the display panel requires a high resolution, a number of channels required for the COF base 3 is increasing. Accordingly, there is an increase in demand for a double-sided COF having circuit wiring patterns on both sides of a flexible board, not a conventional single-sided COF base.
In the case of the double-sided COF, the circuit wiring pattern should be thinly formed on the both sides of the flexible board, and accordingly, cracks due to bending, may occur in a portion 3a where the bending is performed when the double-sided COF base constitutes a device including the display.